add graphbfs in java

Author: akgmage

Graphs/GraphBFS.java

@@ -0,0 +1,63 @@
+/**
+ * The GraphBFS class represents a simple undirected graph using an adjacency list
+ * and provides a breadth-first search (BFS) algorithm to traverse the graph.
+ */
+import java.util.*;
+import java.io.*;
+
+class GraphBFS {
+    private int V; // Number of vertices in the graph
+    private List<Integer> adjacency[]; // Adjacency list to represent the graph
+
+    // Constructor to initialize the graph with the given number of vertices
+    GraphBFS(int v) {
+        V = v;
+        adjacency = new ArrayList[V];
+        for(int i = 0; i < V; i++) {
+            adjacency[i] = new ArrayList<Integer>();
+        }
+    }
+
+    // Method to add an edge between vertices 'u' and 'v' in the graph
+    void addEdge(int u, int v) {
+        adjacency[u].add(v);
+        adjacency[v].add(u);
+    }
+
+    /**
+     * Performs breadth-first search (BFS) starting from the given source vertex 's'.
+     * Prints the vertices in BFS order.
+     * @param s The source vertex from which BFS starts.
+     */
+    void bfs(int s) {
+        boolean[] visited = new boolean[V]; // Array to track visited vertices
+        visited[s] = true; // Mark the source vertex as visited
+        LinkedList<Integer> Q = new LinkedList<Integer>(); // Queue for BFS traversal
+        Q.add(s); // Enqueue the source vertex
+
+        // BFS traversal
+        while(Q.size() != 0) {
+            int current = Q.poll(); // Dequeue the current vertex
+            System.out.print(current + " -> "); // Print the current vertex
+
+            // Visit all neighbors of the current vertex
+            for(int neighbour: adjacency[current]) {
+                if(!visited[neighbour]) {
+                    visited[neighbour] = true; // Mark the neighbour as visited
+                    Q.add(neighbour); // Enqueue the neighbour for further exploration
+                }
+            }
+        }
+    }
+
+    // Main method for testing the GraphBFS class
+    public static void main(String[] args) {
+        GraphBFS g = new GraphBFS(5); // Create a graph with 5 vertices
+        g.addEdge(2, 3); // Add edges to the graph
+        g.addEdge(2, 4);
+        g.addEdge(3, 1);
+        g.addEdge(4, 1);
+
+        g.bfs(2); // Perform BFS starting from vertex 2
+    }
+}